M3 - Globular Star Cluster in Canes Venatici


Copyright 2011 Hap Griffin

Discovered by Charles Messier in 1764, M3 is one of the brightest globular clusters visible to us.  While the brightest star in it is around Magnitude 11, the entire cluster shines at magnitude 6.4 and is easily grasped in binoculars.  Consisting of roughly a half million stars in a sphere 220 light-years in diameter, it is approximately 10 billion years old and orbits our Milky Way galaxy, currently heading towards us with a radial velocity of 90 miles per second.

M3 lies at a distance of 40,000 light years.


Date/Location:    February 18, 2011     Imaging Infinity Observatory    Bethune, SC
Camera: QSI 583wsg
Filters: Astrodon E Series Generation 2 LRGB
CCD Temperature: -20 C
Instrument:    Planewave 12.5" CDK
Focal Ratio:   f/8
Mount: AP-1200
Guiding:    Auto via the QSI camera's built in Off-Axis Guider mirror and an SBIG ST-402 Guider
Conditions:    Cool and clear with nearly full moon
Weather:    60 F, still
Exposure: 54 minutes total (6 x 3 min each in RGB)
Capture: CCDAutopilot 4 w/ Maxim DL Camera Control, focused automatically w/ FocusMax   
Processing:    Frame calibrations, alignment and stacking with ImagesPlus v3.80.  Finishing in Photoshop CS5.